Slate is a finely grained metamorphic rock created from other rocks...
Formed underground from layers of rock formed on top of each other over millions of years, that have sedimented together.
The heavy weight of the rock causes pressure and heat underground, this process changes the rock.
Metamorphic rock does not melt the rock but changes them both chemically and physically.
The movement of the Earths crust by tectonic plate causes some of the heat and pressure, eventually through this movement uplifts closer to the surface.
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